1. Field of the Invention
The present invention relates to a laser beam machining apparatus for machining a work by use of a laser beam.
2. Description of the Related Art
In a semiconductor device manufacturing process, a plurality of regions are demarcated in a surface of a substantially circular disk-like semiconductor wafer by planned dividing lines called streets which are arranged in a lattice pattern, and devices such as ICs and LSIs are formed in the demarcated regions. Then, the semiconductor wafer is cut (diced) along the streets to divide the regions with the devices formed therein, whereby individual semiconductor chips are manufactured. As a method for dividing the wafer such as a semiconductor wafer along the streets, there has been proposed a method in which irradiation with a pulsed laser beam is conducted along the streets in the wafer so as to form laser beam-machined grooves, and the wafer is cut (diced) along the laser beam-machined grooves by a mechanical breaking apparatus (refer to, for example, Japanese Patent Laid-open No. Hei 10-305420).
A laser beam machining apparatus for carrying out the above-mentioned laser beam machining includes a chuck table for holding a work, and a laser beam irradiation means for irradiating the work held by the chuck table with a laser beam. The laser beam irradiation means has a laser beam oscillator for oscillating the laser beam, and a condenser lens for condensing the laser beam oscillated from the laser beam oscillator. In such a laser beam irradiation means, the laser beam incident on the condenser lens is desirably a parallel beam having a predetermined beam diameter. Since the laser beam oscillated from the laser beam oscillator has a divergence angle, therefore, a beam adjusting means for making parallel the laser beam oscillated from the laser beam oscillator is arranged between the laser beam oscillator and the condenser lens.
In carrying out the adjustment by use of the beam adjusting means, it is necessary to receive the laser beam incident on the condenser lens by a light receiving means such as CCD, and to manually operate the beam adjusting means while checking the beam diameter and the divergence angle (parallelism). Therefore, the adjusting work takes a long time.